Vanilloid compounds are characterized by the presence of vanillyl group or a functionally equivalent group. Examples of several vanilloid compounds or vanilloid receptor modulators are vanillin (4-hydroxy-3-methoxy-benzaldehyde), guaiacol (2-methoxy-phenol), zingerone (4-/4-hydroxy-3-methoxyphenyl/-2-butanon), eugenol(2-methoxy4-/2-propenyl/phenol), and capsaicin (8-methy-N-vanillyl-6-noneneamide).
Among others, capsaicin, the main pungent ingredient in “hot” chili peppers, is a specific neurotoxin that desensitizes C-fiber afferent neurons. Capsaicin interacts with vanilloid receptors (VR), which are predominantly expressed in cell bodies of dorsal root ganglia (DRG) or nerve endings of afferent sensory fibers including C-fiber nerve endings [Tominaga M, Caterina M J, Malmberg A B, Rosen T A, Gilbert H, Skinner K, Raumann B E, Basbaum A I, Julius D: The cloned capsaicin receptor integrates multiple pain-producing stimuli. Neuron. 21: 531-543, 1998]. The VR1 receptor was recently cloned. [Caterina M J, Schumacher M A, Tominaga M, Rosen T A, Levine J D, Julius D: Nature 389: 816-824, (1997)] and identified as a nonselective cation channel with six transmembrane domains that is structurally related to the TRP (transient receptor potential) channel family. Binding of capsaicin to VR1 allows sodium, calcium and possibly potassium ions to flow down their concentration gradients, causing initial depolarization and release of neuro-transmitters from the nerve terminals. VR1 can therefore be viewed as a molecular integrator of chemical and physical stimuli that elicit neuronal signals in a pathological conditions or diseases.
There are abundant of direct or indirect evidence that shows the relation between VR1 activity and diseases such as pain, ischaemnia, and inflammatory (e.g., WO 99/00115 and 00/50387). Further, it has been demonstrated that VR1 transduce reflex signals that are involved in the overactive bladder of patients who have damaged or abnormal spinal reflex pathways [De Groat W C: A neurologic basis for the overactive bladder. Urology 50 (6A Suppl): 36-52, 1997]. Desensitisation of the afferent nerves by depleting neurotransmitters using VR1 agonists such as capsaicin has been shown to give promising results in the treatment of bladder dysfunction associated with spinal cord injury and multiple sclerosis [(Maggi C A: Therapeutic potential of capsaicin-like molecules—Studies in animals and humans. Life Sciences 51: 1777-1781, 1992) and (DeRidder D; Chandiramani V; Dasgupta P; VanPoppel H; Baert L; Fowler C J: Intravesical capsaicin as a treatment for refractory detrusor hyperreflexia: A dual center study with long-term followup. J. Urol. 158: 2087-2092, 1997)].
It is anticipated that antagonism of the VR1 receptor would lead to the blockage of neurotransmitter release, resulting in prophylaxis and treatment of the condition and diseases associated with VR1 activity.
It is therefore expected that antagonists of the VR1 receptor can be used for prophylaxis and treatment of the condition and diseases including chronic pain, neuropathic pain, postoperative pain, rheumatoid arthritic pain, neuralgia, neuropathies, algesia, nerve injury, ischaemia, neurodegeneration, stroke, inflammatory disorders, urinary incontinence (UI) such as urge urinary incontinence (UUI), and/or overactive bladder.
UI is the involuntary loss of urine. UUI is one of the most common types of UI together with stress urinary incontinence (SUI) which is usually caused by a defect in the urethral closure mechanism. UUI is often associated with neurological disorders or diseases causing neuronal damages such as dementia, Parkinson's disease, multiple sclerosis, stroke and diabetes, although it also occurs in individuals with no such disorders. One of the usual causes of UUI is overactive bladder (OAB) which is a medical condition referring to the symptoms of frequency and urgency derived from abnormal contractions and instability of the detrusor muscle.
There are several medications for urinary incontinence on the market today mainly to help treating UUI. Therapy for OAB is focused on drugs that affect peripheral neural control mechanisms or those that act directly on bladder detrusor smooth muscle contraction, with a major emphasis on development of anticholinergic agents. These agents can inhibit the parasympathetic nerves which control bladder voiding or can exert a direct spasmolytic effect on the detrusor muscle of the bladder. This results in a decrease in intravesicular pressure, an increase in capacity and a reduction in the frequency of bladder contraction. Orally active anticholinergic drugs such as propantheline (ProBanthine), tolterodine tartrate (Detrol) and oxybutynin (Ditropan) are the most commonly prescribed drugs. However, their most serious drawbacks are unacceptable side effects such as dry mouth, abnormal visions, constipation, and central nervous system disturbances. These side effects lead to poor compliance. Dry mouth symptoms alone are responsible for a 70% non-compliance rate with oxybutynin. The inadequacies of present therapies highlight the need for novel, efficacious, safe, orally available drugs that have fewer side effects.
WO 00/50387 discloses the compounds having a vanilloid agonist activity represented by the general formula:
wherein;    XP is an oxygen or sulfur atom;    AP is —NHCH2— or —CH2—;    Ra is a substituted or unsubstituted C1-4 alkyl group, or Ra1CO—;            wherein        Ra1 is an alkyl group having 1 to 18 carbon atoms, an alkenyl group having 2 to 18 carbon atoms, or substituted or unsubstituted aryl group having 6 to 10 carbon atoms;            Rb is a hydrogen atom, an alkyl group having 1 to 6 carbon atoms, an alkoxy group having 1 to 6 carbon atoms, a haloalkyl group having 1 to 6 carbon atoms or a halogen atom;    RC is a hydrogen atom, an alkyl group having 1 to 4 carbon atom, an aminoalkyl, a diacid monoester or α-alkyl acid; and    the asteric mark * indicates a chiral carbon atom, and their pharmaceutically acceptable salts.
WO 2000/61581 discloses amine derivatives represented by the general formula:
wherein    (R′, R″) represent (F, F), (CF3, H), or (iPr, iPr)as useful agents for diabetes, hyperlipemia, arteriosclerosis and cancer.
WO 00/75106 discloses the compounds represented by the general formula:
wherein    Z represents
     in which            R90 is hydrogen, C1-12 alkyl, C3-8 cycloalkyl, or the like, and R91 is amino-C1-6 alkyl, aminocarbonyl-C1-6 alkyl, or hydroxyaminocarbonyl C1-6 alkyl; and        R90 and R91 are independently selected from the group consisting of H, C1-6 alkyl, C1-6 alkylthio, C1-6 alkoxy, fluoro, chloro, bromo, iodo, and nitro;as useful agents for treating MMP-mediated diseases in mammals.        
WO 00/55152 discloses the compounds represented by the general formula:
wherein    Ar1 is heterocycle;    Ar2 is tetrahydronapthyl;    X0 is O or S; and    L and Q are defined in this specification;    as useful agents for treating inflammation, immune related disease, pain and diabetes.
However, none of these reference discloses simple tetrahydro-naphthalene derivatives having VR1 antagonistic activity.
The development of a compound which has effective VR1 antagonistic activity and can be used for the prophylaxis and treatment of diseases associated with VR1 activity, in particular for the treatment of urinary incontinence, urge urinary incontinence, overactive bladder as well as pain, and/or inflammatory diseases such as asthma and COPD has been desired.